This invention relates to refrigeration systems and more specifically to refrigeration systems with independent compartment temperature control.
Household refrigerators typically operate on a simple vapor compression cycle. Such a cycle typically includes a compressor, a condenser, an expansion device and an evaporator connected in series and charged with a refrigerant. The evaporator is a specific type of heat exchanger that transfers heat from air passing over the evaporator to refrigerant flowing through the evaporator, thereby causing the refrigerant to vaporize. The cooled air is then used to refrigerate one or more freezer or fresh food compartments.
Household refrigerators are expected to operate over a range of ambient temperatures, typically from about 55.degree. F. to about 90.degree. F. System users are typically supplied control knobs to adjust Fresh Food and Freezer compartment temperatures. At each combined setting of the control knobs, there is a target set of Fresh Food and Freezer temperatures that an ideal refrigerator should achieve, independent of ambient conditions. Different hardware and control strategies attempt to approximate this ideal performance matrix.
Typically a control device is used to regulate airflow to the fresh food compartment to account for the changing load split between freezer and fresh food sections. During high ambient temperature and frequent fresh food access, more airflow to the fresh food section is required to maintain target temperatures. Manual damper air control cannot automatically compensate for changing loads and is prone to customer misadjustment. Motorized damper airflow modulation, powered by a system controller, is prone to malfunction (i.e. freeze up) and may cause adverse temperature gradients during low ambient operation.
Accordingly, there is a need in the art for an improved refrigeration system for achieving ideal performance temperatures of fresh food and freezer compartments.